Endotracheal tubes are frequently used for the primary purpose of ensuring that a patient's airway remains clear, which secondarily provides access to the bronchial tree for the aspiration of secretions. However, due the fact that the intubation device is a tube placed within the body passageway, the natural lumen or size thereof is necessarily reduced, although the narrower tube lumen is expected to be clear. This leads to a specific problem. The problem is that most if not all conventional endotracheal tubes kink when subjected to normal body temperature which significantly increases the work of breathing. An inflatable cuff near a distal end of the intubation device is inflated once the tube is intubated for holding the tube in place. The inflatable cuff seals the tube to the body passageway so that all of the air passing to and from the patient's lungs must pass through the tube. The inflated cuff, in position, also forms a space above the cuff and between the intubation device and the body passageway within which secretions and bacteria, or the like, will accumulate. The seal of the inflatable cuff advantageously prevents the accumulated secretions from passing into the patient's lungs so long as the cuff remains fully inflated. Nevertheless, the secretions that build up within this space may cause harm to the patient.
For the above reason, a suction tube is included to remove the secretions and bacteria that collect above the cuff. Then, when the intubation device is intubated within the respiratory tract, the tube passes into the trachea through the epiglottis and as a result the epiglottis cannot then close. Thus, the salvia from the mouth can pass and become trapped in the larynx and trachea. Moreover, other secretions that are produced by the body are trapped as well. The large amount of secretions and bacteria that collect in the space above the cuff could be drawn into the patient's lungs during coughing, cuff deflation, or extubation (i.e. tube removal). This not only presents an immediate danger to the patient's ability to breath, but is believed to substantially increase the chance that the patient will develop aspiration pneumonia.
Thus, it has become desirable to find ways for removing the secretions and bacteria that collect above the cuff during the time period of intubation. Typically, such removal includes the application of suction to the above-the-cuff region for the removal of collected secretions. The initial solution was simply to periodically insert a suction catheter along with the intubation device once intubated and sealed by the cuff to suction out accumulated secretions. As a modification to this procedure, it is presently known to provide an intubation device including an integrally formed suction catheter with an opening in and above-the-cuff region through which periodic or constant suction can be applied for removal of secretions after intubation located on the greater or outer side of the tube.
An improved intubation device is disclosed in my earlier U.S. Pat. No. 5,697,365, which is incorporated herein in its entirety by reference. As disclosed in my earlier U.S. Patent there are many types of endotracheal tubes known to the medical profession and many types of known apparatus for keeping the tubes in place in a patient's oral cavity and trachea. However, it is has been found that a number of these tubes may have life threatening consequences. One of the most serious consequences is the deficiencies of the materials selected for use in the manufacturing of the tubing. Some of the plastic materials used for making endotracheal tubing are not heat stable in their physical characteristics at body temperature and do not remain firm enough at those temperatures to retain their desired shapes while being inserted and while in place. Sometimes the tubing will collapse and/or kink significantly reducing the rate of flow of air, oxygen mixture, etc. that can flow through the tube. The total volume of fluid flow per unit of time through a tube is give by Poiseuille's law as follows:
                    ⅆ        V                    ⅆ        t              =                  π        8            ⁢                        R          4                n            ⁢                        (                                    p              1                        -                          p              2                                )                L              ,where
V=Volume of flow.
R=radius of the tube
p1 and p2 are the pressures at the respective ends of the tube.
N=viscosity of the flowing fluid.
L=the length of the tube.
            ⅆ      V              ⅆ      t        ⁢          ⁢  is  ⁢          ⁢            rate of flow              change in time      
From this equation it is seen that any slight restriction in the radius R of the tube can have a significant reduction in the rate of flow through the tube since the radius is raised to the fourth power and adversely affects the work of breathing.
Additionally, it is seen that the rate of flow is inversely proportional to the length of the tube. Therefore, for a weak patient who does not have the strength to overcome any significant resistance to breathing, not only must the tube remain uniform in cross section throughout its length, but the tube must be as, short as possible.
Additionally as disclosed in my earlier patent, an endotracheal tube construction includes an elongated kink resistant flexible tubular member having distal and proximal ends with a curved portion there between. The tubular member defines a major passageway or airway and a relatively small cuff inflating lumen which is parallel to a major passageway and disposed at the end of the tubular member. The cuff inflating lumen is positioned within a portion of the wall which is subjected to tension (the greater curvature) as the tubular member is bent as opposed to being positioned in the portion of the wall that is under compression (the lesser curvature). In addition, the portion of the wall adjacent to the lumen may be thicker than the wall in other portions of the tube, a D-shaped reinforcement so that the tube is less likely to kink or collapse during intubation of a patient.
The endotracheal tube preferably includes a bevel tip and is constructed and arranged so that the bevel tip can be rotated by twisting a portion of the tube which extends out of a patient's mouth or nose without kinking or collapsing the tube. In this way, the far end of the suction catheter can be biased in the direction of the selected bronchi. A second minor passageway or lumen is also parallel to a central passageway and disposed in the same portion i.e. (the wall of greater curvature) of the tubular member.
Notwithstanding the above, it is presently believed that there is a need and a potential commercial market for an improved endotracheal tube and inflatable cuff with an improved construction. There should be a need and a commercial market for such endotracheal tubes because they are properly centered and facilitate accumulation and removal of bacteria and secretions from above the cuff. In addition, such tubes are durable and less likely to kink then conventional tubes. Further, the construction of the cuff not only facilitates the centering of the tube but reduces the likely hood of the tapered end being off center. Still further, the endotracheal tube has a reinforced side on the portion of lesser curvature to prevent or at least reduces the likelihood of kinking.